Crystal Vision
Introduction
1 Introduction
The ADCA412 is a dual analogue to digital audio converter designed to convert two dual
channel analogue audio inputs to two AES/EBU audio outputs. The module accepts either
525 or 625 references from analogue composite video, word clock or an AES reference.
There are two operational modes ‘Auto’ that allows flexible phase locked loop sample
rate control to accept a wide reference input frequency range and ‘Xtal’ that allows for
crystal locked operation at 48kHz.
In addition to analogue to digital conversion, the ADCA412 incorporates a number of
powerful features. For example, a channel swap function allows channels 1 and 2 to be
transposed, whilst the phase of the right hand channel can be inverted to correct phasing
errors. Analogue monitoring can be used to listen to each incoming stereo pair.
Also ‘near silence’ detectors monitor the audio signal level in both channels in case they
fall below –50dBFS for more than a selected period of time. Silence warning and loss of
reference warning status are normally routed by default to the GPI port for each channel.
The main features are as follows:
•
20/24 bit dual analogue to digital audio converter
•
+12dBu to +28dBu input level for 0dBFS digital output with input level pre-sets
for +18dBu and +24dBu
•
110 Ohm balanced and 75 Ohm unbalanced output versions via sub-module
option
•
choice of rear connectors to accommodate I/O format options
•
external reference accepts video, word clock or AES source
•
clock regeneration for 48kHz even when locked to video
•
automatic 525/625 operation with AES phase adjustment in 625
•
wide ranging ‘Auto’ mode for sample rates between 30kHz and 50kHz when
using AES reference outside 48kHz +/- 50 ppm
•
precision, re-clocking ‘Xtal’ mode for 48kHz output sample rate when locked to
any 48kHz reference
•
channel swap and RH channel invert
•
loss of reference input and sustained silence warning via indicators and external
alarms
•
GPIs for ‘Xtal’ and ‘Auto’ mode change, channel swap and loss of input/silence
warning
•
control and status monitoring via board edge, frame/remote control panel and
Statesman
ADCA412 User Manual R2.1
3
30 October 2018
